The term “fibre” as used herein comprises staple fibres and continuous filaments which can be produced by principally known spinning processes such as dry spinning, wet spinning or melt spinning.
These spinning processes are described for example in Polyurethanhamstofffasern, H. Gall and M. Kausch in Kunststoff-Handbuch 7, Polyurethane, editor: G. Oertel, Carl Hanser Verlag Munich Vienna, 1993, pages 679 to 694.
Elastic polyurethaneurea fibres composed of long-chain synthetic polymers that are constructed to an extent of at least 85% of segmented polyurethanes based for example on polyethers, polyesters and/or polycarbonates are well known. Yarns composed of such fibres are used for producing fabrics which in turn are useful inter alia for foundation garments, stockings and sportswear, examples being bathing costumes and swimming trunks.
Polyurethaneurea fibres possess outstanding elasticity and substantial extensibility combined with high resiling forces. Owing to this outstanding combination of properties, they are widely used in the apparel sector. When used to produce dark textiles in the apparel sector which are elasticized through polyurethaneurea fibres, it is difficult to obtain a uniform coloration or visual appearance of the various yarns. The reason is that the various yarns used for producing the textile have different hues. If, for example, the inelastic yarn has a dark hue, a conventionally used elastic polyurethaneurea fibre will become visible in the textile and “grin through” and thus disrupt the visual appearance of the textile. Another method of producing dark textiles in the apparel sector which are elasticized through polyurethaneurea fibres is dyeing with the desired dye. However, dyeing is a technically inconvenient, additional and hence also cost-raising process step in the manufacturing chain of the textile.
The literature describes a method of producing a dark polyurethaneurea fibre.
As described in the KR-A-2002092588 application, a black polyurethaneurea fibre is obtainable by incorporating graphite as an additive. True, the polyurethaneurea fibres thus obtained are coloured and have a black colour, but the incorporation of carbon black in polyurethaneurea fibres very quickly gives rise to agglomerates which disrupt the spinning operation by clogging filters. Furthermore, the agglomeration of the carbon black may disrupt its disbursement in the fibre to such an extent that the fibre is no longer consistent in thickness. This can lead to a dishomogeneous colour for the fibre and also to broken ends in the further processing into textiles.
As described in DE-A-10 2004 003 997, a dark polyurethaneurea fibre may be obtained by incorporating dark spinel pigment based on iron oxide as an additive. True, the polyurethaneurea fibres thus obtained are coloured and have a dark colour, but their processing properties to produce the fibres are not good enough. For instance, metering pumps metering the solutions comprising the hard spinel pigments may become damaged by abrasion. Thus, the incorporation of dark spinel pigment based on iron oxide as an additive in a polyurethaneurea composition cannot be done constantly over a long period. Owing to metering fluctuations, levels of spinel pigment in the polyurethaneurea fibre will vary and generally become ever lower. This can result in ever lighter polyurethaneurea fibres which on further processing of the fibres into textiles then can lead to undesirable differences in colour.
The present invention, then, has for its object to provide dark polyurethaneurea fibres which do not have the aforementioned disadvantages of the polyurethaneurea fibres described above. The spinning operation to produce the polyurethaneurea fibre shall not be disrupted through the formation of agglomerates in the spinning solution for example. Nor shall any change in hue occur during the production of the polyurethaneurea fibre, nor during the processing of the polyurethaneurea fibre in the textile processing chain and in the use of the finished articles.